1. Field of the Invention
The present invention relates to headsets for bicycles as are used for rotationally mounting the steerer tube of the bicycle front fork in the head tube of the bicycle frame.
2. Description of Related Art
Head sets of the so-called threadless type are well known, U.S. Pat. Nos. 5,095,770 and 6,651,525 being examples of such head sets. Typical of this type of headset is the fact that a compression member having a part with a wedge-shaped cross-section is inserted between the bearing race and the steerer tube with an axial load being applied so as to take up the clearance between the steerer tube and the bearing race so as to secure the bearing race to the steerer tube, as well as to axially preload the bearings. However, while bicycle front forks are manufactured with steerer tubes of standard outer diameter sizes (O.D.), the steerer tube is not a precision manufactured product so that significant tolerance variations can and do occur. If the O.D. variation is on the plus side, the fact that it is somewhat too large poses no problem since it simply means that the wedge-shaped portion of the compression ring merely has to be pressed into the bearing race clearance to a lesser extent in order to obtain the necessary fixation and preload. On the other hand, should the O.D. be too small, such does pose a problem since it may not be possible for the wedge-shaped portion to be inserted far enough into the clearance gap to produce the necessary holding forces and bearing preload before the top cap of the head set engages the top of the bearing cup and/or bearing.
The use of shims is generally known for taking up slack in parts of various types. In the headset field, cylindrical shims, sometimes referred to as reducers are known, e.g., for adapting a head set intended for a 1-⅛″ to a 1″ steerer tube or 1-¼″ head set to a 1-⅛″ steerer tube. These shims are inserted over the steerer tube and must be held between the bearing race and the steerer tube during installation. Such an operation is difficult for one person and such shims are based on the assumption that the steerer tube O.D. is correct.
It has also been suggested to place a washer-like shim between the top cap of the head set and bearing race to prevent drag on the bearing cup during turning of the steerer tube. However, it can be difficult to properly position such a shim during installation and to maintain such a shim in its proper position during use if the shim has an inner diameter (I.D.) that is larger than the O.D. of the steerer tube, and thus, can slide radially. Furthermore, when it becomes necessary or desirable to disassemble the steering assembly, e.g., to lubricate or replace the bearings, or to change the fork or during traveling, the shims can become lost or misplaced, and thus, the height setting achieved is lost.